Agilent Technologies 8510-58 manual Introduction, Measurement errors, Measurement calibration

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Introduction

This product note covers measurement calibration requirements for the Agilent 8510B/C network analyzer. All of the capabilities described in this note also apply to the Agilent 8510A with the following exceptions: response & isolation calibra- tion; short circuit inductance; class assignments for forward/reverse isolation, TRL thru, reflect, line and options; and adapter removal.

Measurement errors

Measurement errors in network analysis can be separated into two categories: random and system- atic errors. Both random and systematic errors are vector quantities. Random errors are non-repeat- able measurement variations and are usually unpredictable. Systematic errors are repeatable measurement variations in the test setup.

Systematic errors include mismatch and leakage signals in the test setup, isolation characteristics between the reference and test signal paths, and system frequency response. In most microwave measurements, systematic errors are the most sig- nificant source of measurement uncertainty. The source of these errors can be attributed to the sig- nal separation scheme used.

Figure 1. Agilent 8510 full 2-port error model

The systematic errors present in an S-parameter measurement can be modeled with a signal flow- graph. The flowgraph model, which is used for error correction in the 8510 for the errors associated with measuring the S-parameters of a two port device, is shown in the figure below.

The six systematic errors in the forward direction are directivity, source match, reflection tracking, load match, transmission tracking, and isolation. The reverse error model is a mirror image, giving a total of 12 errors for two-port measurements. The process of removing these systematic errors from the network analyzer S-parameter measurement is called measurement calibration.

EDF, EDR-Directivity

ELF, ELR-Load Match

ESF, ESR-Source Match

ETF, ETR-Trans. Tracking

ERF, ERR-Refl. Tracking

EXF, EXR-Isolation

Measurement calibration

A more complete definition of measurement cali- bration using the 8510, and a description of the error models is included in the 8510 operating and programming manual. The basic ideas are summa- rized here.

A measurement calibration is a process which mathematically derives the error model for the 8510. This error model is an array of vector coeffi- cients used to establish a fixed reference plane of zero phase shift, zero magnitude and known impedance. The array coefficients are computed by measuring a set of “known” devices connected at a fixed point and solving as the vector difference between the modeled and measured response.

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Contents Product Note 8510-5B Table of contents Measurement errors IntroductionMeasurement calibration Calibration kit Class assignment Standard definitionStandard definitions table Standard class assignments Select standards Modification procedureStandard definition models Define standardsStandard number Standard typeOpen circuit capacitance C0 , C1 , C2 and C3 ΠfZ ΠfXShort circuit inductance L0 , L1, L2 and L3 ∆∅radians = 2πf ∆lengthTerminal impedance Offset delayDelay seconds = Fixed or slidingOffset Z0 Linear delay Actual delay = Fco/f210 log10e εr Offset loss1GHz = 1GHz c Z0Lower/minimum frequency ∅radians = Upper/maximum frequencyFupper = 2 x Flower Coax or waveguideAssign classes Standard labelsStandard Classes Isolation S11 A,B,C and S22 A,B,CForward transmission match and thru Reverse transmission match and thruTRM Thru TRL ThruTRL Reflect TRL LineStandard Class labels TRL optionsCalibration kit label Verify performance Enter standards/classesModeling an arbitrary impedance standard User modified cal kits and Agilent 8510 specificationsModification examples Modeling a thru adapterTo store calibration kits from the Agilent 8510 onto a disk Appendix a Calibration kit entry procedureDisk procedure To load calibration kits from disk into AgilentFront panel procedure P-band waveguide example Pshort Appendix B Dimensional considerations in coaxial connectors Mm coaxial connector interfaceType-N coaxial connector interface Female type-N Mm Coaxial connector Type-N coaxial connector interfacePage Equation Appendix C Cal coefficients modelTheir first order approximations, R is small and G=0, are Then Online assistance Phone or Fax United States
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